How to bake multiple sounds to f-curve to the same object
Pushing Down (or Stashing) to the NLA




Bake your fcurve as you've done.


Give the action a meaningful name, I've switched to dope sheet shape key editor mode to do this. Can push down / stash / rename directly from the NLA editor too.
Hit the push down button
Switch to the NLA editor and move your strip where you wish to play in the timeline.



Consult the docs re the difference between push down and stash, and other info re using the NLA Editor.


Repeat.  Notice in image above I have already done this once.. with the previous bake "MyAction.001".


Custom Properties and drivers.

How to bake multiple audio sounds to f curve?

A suggestion is add a speaker, parent it such that it sticks out the mouth. When a speaker has a sound loaded it is loaded as an audio strip in the NLA. It never has the correct length. Match it to the length of your sound bake for that sound.



SoundAction is a baked sound on a custom property on a speaker.
NLAStrip (in aqua) is the sound the speaker plays resized to match.

I used this concept for the now defunct sound drivers addon. https://blender.stackexchange.com/a/39241/15543  

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